It is one of life’s mysteries: Individuals or groups that wish to be taken seriously insist that the Holocaust never happened, that it was in fact an invention of Jews seeking to advance their own selfish interests at the expense of others.

Serious historians dismiss such claims, yet Holocaust deniers — they prefer to be called “revisionists” (a more respectable term in an academic context) — see the allegations against Hitler and his henchman as a hoax. Given what that tells us about human nature, is it any wonder that conspiracy theorists inevitably surface after events such as 9/11 or the Branch Davidian siege of 1993?

Well, as bad as most of us believed the Holocaust was, it has now been learned that it was actually much worse. A new study, publicized last week, indicates that under Hitler’s direction German authorities brutalized minorities — the Jews were only the most numerous and prominent of them — on a scale surpassing what was previously known.

“The numbers are so much higher than what we originally thought,” said Hartmut Berghoff, director of the German Historical Institute in Washington. “We knew before how horrible life in the camps and ghettos was, but the numbers are unbelievable.”

Berghoff was referring to data collected by researchers who have identified 42,500 Nazi ghettos and camps in Germany and in German-controlled areas from France to Russia. The persecution began after Hitler seized power in 1933 and lasted until Germany was defeated in 1945.

“The figure is so staggering that even fellow Holocaust scholars had to make sure they had heard it correctly when the lead researchers previewed their findings at an academic forum in late January,” The New York Times reported Saturday.

The documented camps, the report continued, included “killing centers” and thousands of labor camps where prisoners were forced to manufacture war supplies for the German military, prisoner-of-war camps, sites the Nazis arrogantly referred to as “care centers” (where pregnant women were forced to have abortions or their babies were killed after birth), and brothels, where women were forced to have sex with German troops.

In the public’s mind, the most notorious concentration camps — Auschwitz, for instance — may usually represent Hitler’s killing machine just as imprisonment of entire Jewish families in ghettos (such as Warsaw, where in 1943 there was a famous and bloody uprising) have drawn widespread attention. But, the new report argues, these more famous sites represent but a fraction of the entire Nazi program.

“The maps the researchers have created to identify the camps and ghettos turn wide sections of wartime Europe into black clusters of death, torture and slavery — centered in Germany and Poland, but reaching in all directions,” the newspaper noted.

Geoffrey Megargee, the lead researcher on the project, said it changes how Holocaust scholars understand the way camps and ghettos evolved. The process began in 1933 as the government established about 110 camps to hold an estimated 10,000 political opponents and others, the researchers found.

As Germany began occupying its European neighbors, the use of camps and ghettos expanded to confine and sometimes kill not just Jews but also homosexuals, Gypsies, Poles, Russians and other ethnic groups. Researchers learned that these camps and ghettos varied in their mission, organization and size, depending on the Nazis’ needs.

It would be comforting to believe that Germany’s defeat in World War II had taught the world a lesson, yet to this day there are examples of outrageous government-sponsored brutality around the world. The human race, sad to say, appears unable to learn from history.